Cirrus Logic CS485xx - Manual (Page 6)

6 DS734F5
3 Code Overlays
3 Code Overlays
The suite of software available for the CS485xx family consists of an operating system (OS) and a library of overlays. The
overlays have been divided into three main groups called Matrix-processors, Virtualizer-processors, and Post-processors.
All software components are defined below:
1. OS/Kernel—Encompasses all non-audio processing tasks, including loading data from external memory,
processing host messages, calling audio-processing subroutines, error concealment, etc.
2. Matrix-processor—Any Module that performs a matrix decode on PCM data to produce more output channels
than input channels (2 n channels). Examples are Dolby ProLogic IIx and DTS Neo:6. Generally speaking, these
modules increase the number of valid channels in the audio I/O buffer.
3. Virtualizer-processor—Any module that encodes PCM data into fewer output channels than input channels (n 2
channels) with the effect of providing “phantom” speakers to represent the physical audio channels that were
eliminated. Examples are Dolby Headphone
® and Dolby Virtual Speaker ® . Generally speaking, these modules
reduce the number of valid channels in the audio I/O buffer.
4. Post-processors—Any module that processes audio I/O buffer PCM data in-place after the matrix- or
virtualizer-processors. Examples are bass management, audio manager, tone control, EQ, delay,
customer-specific effects, etc.
The bulk of each overlay is stored in ROM within the CS485xx, but a small image is required to configure the overlays and
boot the DSP. This small image can either be stored in an external serial FLASH/EEPROM, or downloaded via a host
controller through the SPI
™ /I 2 C ™ serial port.
The overlay structure reduces the time required to reconfigure the DSP when a processing change is requested. Each
overlay can be reloaded independently without disturbing the other overlays. For example
, when a new matrix-processor
is selected, the OS, virtualizer-, and post-processors do not need to be reloaded — only the new matrix-processor (the
same is true for the other overlays).
Table 3-1 lists the firmware available based on device selection. Refer AN298, CS485xx Firmware User’s
Manual for the latest listing of application codes and Cirrus Framework ™ modules available.
Table 3-1. Device and Firmware Selection Guide
Device Suggested Application Channel Count Input/Output Package
CS48520-CQZ Digital TV, portable audio docking station, portable DVD, DVD mini/
receiver, multimedia PC speakers
Up to 4-channel in/4-channel out 48-pin QFP
CS48540-CQZ
CS48540-DQZ CS48520 features plus 8-channel car audio, DVD receiver Up to 8-channel in/8-channel out 48-pin QFP
CS48560-CQZ
CS48560-DQZ CS48540 features plus 12-channel car audio, high-end digital TV, dual
source/dual zone SACD Up to 12-channel in/12-channel out 48-pin QFP